Within these multi-access networks, certain interface technologies are able to implement the mechanism of paging, that is to say the broadcasting of search requests for mobile nodes in a set of cells within which a terminal can move without signaling this explicitly to the network, that is to say in a location zone. A terminal not having any communications in progress can switch to a standby state and move within its location zone without the network knowing precisely in which cell it is situated. The objective of paging is to save the resources of the terminal and of the network (such as for example radio resources, the network signaling, etc.).
The terminal in the standby state merely listens to and interprets certain announcements of the network such as the paging requests and the broadcasting of location zone identifiers. This information is broadcast in a manner specific to each technology considered, for example by using dedicated logical channels. The terminal is required to update its location with each change of location zone, as well as in a periodic manner. Each location update involves exiting the standby state, to which the terminal can nonetheless return immediately afterwards. When the terminal receives a paging request intended for it, it implements a location updating procedure making it possible to locate it in its current cell. It therefore becomes located with enough precision so that the network can route the traffic intended for it.
However, not all technologies allow the implementation of the paging mechanism. In particular, “WiFi” wireless (802.11) technologies do not make it possible to implement this process. When the terminal moves between two 802.11 cells, it must therefore systematically become associated with the access point of the new cell which it is entering in order to remain reachable, even if it does not have any traffic session in progress.
Within the framework of multi-access networks, the problem of the saving of the resources of the terminal and network therefore persists, since not all technologies are suited to the implementation of the paging mechanism and it is consequently difficult for example to save the resources of a multi-access terminal in a multi-access network. The same holds in networks which implement only one technology (one then speaks of single-technology networks), when this technology does not allow the implementation of the paging mechanism.
Moreover, in a multi-access network, it is complicated to manage paging requests for each possible interface of the multi-access terminal, so that it is almost impossible for the latter to be placed in the standby state.
In order to expand paging mechanisms to multi-access networks and terminals, various works have been published. A new approach to paging for multi-access environments has in particular been proposed. Such an approach relies on the cooperation between the multi-access access networks and a centralized network element, called the “Paging Center”. Two processes are provided for in this approach:                a process based on registration “Registration based approach” in which the “Paging Center” maintains the state of the interfaces of the mobile terminals. To reach a terminal (NM), the network contacts the “Paging Center” which selects the access network to be used and can trigger the paging;        a process which is not based on registration “Non registration based approach” in which the “paging center” triggers pagings “blindly” on one or more access networks so as to try to reach the terminal. When the terminal receives the paging, it selects one of the access networks to send its response to the “paging center”.        
Interface-based maintaining of the states of the mobile such as envisaged in this document poses at least two types of problems: it generates the use of complex location contexts (at the minimum, maintaining of one context per interface used on the terminal) as well as the use of signalings dedicated to each technology. Moreover, the “paging center” also poses scale-up problems: the “paging center” centralizing the data streams destined for the terminals on standby potentially becomes a point of congestion in the network, particularly when it involves managing several hundreds of thousands of terminals.
In the case of implementation of the approach which is not based on registration “Non registration based approach”, the solution provided for by the aforementioned approach consumes an enormous amount of resources at the network level, this not being acceptable.
Moreover, the proposed approach does not afford any response to the problem posed by the technologies which are not able to implement the paging mechanism, such as WiFi technologies.
There therefore exists a requirement for a technique allowing the implementation of a paging mechanism, both in a single-technology network when the technology implemented in this network does not a priori allow the implementation of such a mechanism, and in a multi-access network in which at least one of the deployed technologies is not able to implement such a paging mechanism.